Polycarbonate polymers are well-known as excellent molding materials. Products made from polycarbonate polymers exhibit such properties as high impact strength, toughness, high transparency, excellent properties within wide temperature limits, good dimensional stability, good creep resistance and the like. It is also desirable to provide polycarbonate polymers having improved flame retardance so that products made from such polycarbonate polymers can be safely used by the consumer and also meet the increasing requirements of certain flame retardant criteria being established by local and federal government agencies as well as the manufacturers of such products. One such polycarbonate composition having improved flame retardance is disclosed in U.S. Pat. No. 4,182,838 where halogenated vinylidene diphenols are used to prepare high molecular weight aromatic polycarbonates. Other halogenated polycarbonates have also been obtained by using halogenated monomers as the main polymer building block. Examples of such polycarbonate compositions include tetrabromobisphenol-A and (3,3'-dichloro-4,4'-dihydroxy-diphenyl)-methane monomer as disclosed in U.S. Pat. No. 3,028,365.
Fluorine-containing polyarylates are described in a paper published in Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1649-1654, September, 1965 (Chemical Abstracts 64, 8321h (1966). Polyesters of terephthalic acid isophthalic acids with 4,4'-(hexafluoro-isopropylidene)diphenol and with 4,4'-[alpha(trifluoromethyl)benzylidene]diphenol were synthesized, and it was found that the replacement of CH.sub.3 groups on the central carbon atom of the isopropylidene diphenol and the benzylidene diphenol by CF.sub.3 groups leads to a lowering of the softening points of the polyesters based thereon. Similar monomers are described in Netherlands patent application No. 6,407,548 filed July 2, 1964, and opened for inspection on Jan. 4, 1965. The Netherlands disclosure relates to a process for the preparation of polycarbonate resin by reacting phosgene with 2,2-bis(p-hydroxyphenyl)-1,1,3,3-tetrafluoro-1,3-dichloropropane. It was disclosed therein that the polycarbonate resin had good thermal stability and low vapor permeability. The monomers in the foregoing references were prepared from the corresponding ketones and phenol, and in all cases, the positions on the central carbon atom of the diphenol have been substituted with halogenated methyl groups or halogenated methyl groups in combination with phenyl groups.
In U.S. Pat. No. 3,388,097, 4,4'-(1,1,1-tri-fluoroethylidene)diphenol was made from trifluoroacetaldehyde hydrate and phenol in the presence of anhydrous hydrogen fluoride in a Hastelloy bomb. The product was distilled under reduced pressure at 165.degree.-170.degree. C. and 0.5-0.6 mm. Hg. Polyesters were made from these perhaloalkyl bisphenols and specified aromatic acid halides. However, it is noted that the acid catalyst is anhydrous hydrogen fluoride which has to be handled in a special alloy bomb, and that the reaction product had to be distilled at 165.degree.-170.degree. C. at reduced pressure. The bisphenols which are disclosed for making polyesters in U.S. Pat. No. 3,388,097, have the structure: EQU HO--Ar.sub.1 --Z--Ar.sub.1 --OH (1)
wherein Ar.sub.1 is para-phenylene, and Z is a divalent radical having the formula: ##STR1## wherein R and R' may be the same or different and represent perhalogenated lower alkyl groups, fluorine and chlorine being the preferred halogen species, with the provision that R' may represent hydrogen when R represents a perfluorinated lower alkyl group. These bisphenols are prepared by the anhydrous hydrogen fluoride catalyzed condensation of an appropriate halogenated ketone or aldehyde with two molecules of an appropriate phenol. However, there is no suggestion of high molecular weight aromatic polycarbonates or of improved flame retardance of the polyesters derived from the fluorinated diphenols.
In U.S. Pat. No. 4,220,583, flame retardancy of polycarbonate compositions was improved by admixing a halogen-free aromatic polycarbonate and minor amounts of partially fluorinated polyolefin and minor amounts of an organic alkali metal salt or an organic alkaline earth metal salt, or mixtures thereof. Although these polycarbonate compositions containing flame retardant organic salts exhibit good flame retardancy, it is always desirable to achieve flame retardancy without resorting to additives, especially when transparent compositions are required.
In general, the prior art references recognize that flame retardance can be imparted to polycarbonates made from brominated or chlorinated monomeric building blocks. None of these references, however, discloses or suggests that a high molecular weight polycarbonate resin having improved flame retardance can be obtained from fluorinated diphenols.